Strokes can be devastating, but can some of them be prevented? This edition of Healthwatch takes a close look at some research that asks whether timely medical attention after the occurrence of warning symptoms can substantially reduce the risk of going on to a stroke.

Cerebrovascular accidents, commonly known as strokes, exact an enormous toll on society and are a leading cause of reduced capacities and death. In Canada, more than 50,000 strokes occur annually and more than 16,000 people die each year from their effects. Worldwide, 15 million strokes occur annually and stroke is thus the greatest cause of acquired disability.

Transient ischemic attacks – TIAs – are cerebrovascular events that are sometimes a warning of an impending stroke. A TIA is a short-term lack of blood supply to the brain and is a serious warning sign. TIAs are thus commonly referred to as “warning strokes” and also as “mini strokes,” although this latter term is less accurate, because these episodes produce stroke-like symptoms but no lasting damage.

As with heart attacks, warning strokes can go unnoticed if one is not aware of the signs and symptoms. Again, like heart attacks, warning strokes and strokes (brain attacks) can be effectively treated, and recognizing them is key to increasing the likelihood of getting urgent treatment.

Roughly 30 to 40 per cent of people with a stroke caused by reduced blood flow (ischemic stroke) report having had a warning-stroke. Recent studies have revealed that after a warning stroke, the risk of having a stroke in the next 90 days is about 10 per cent. About half of these strokes occur within the first two days after a warning stroke.

What are the signs and symptoms of a warning stroke or stroke?

Warning strokes and strokes are often characterized by one or more of five key signs and symptoms:

– Sudden loss of strength or numbness in the face, arm or leg.

– Difficulty speaking and/or understanding; confusion.

– Sudden vision impairment.

– Severe and unusual headache.

– Dizziness, especially when accompanied by any of the other four symptoms.

The study

Early use of existing preventive strategies for stroke (EXPRESS) study, by Peter Rothwell et al, The Lancet, October 2007.

What question did this study attempt to answer?

While it is well recognized that the risk of developing a stroke over the long term can be reduced by meticulous attention to blood pressure and cholesterol control, the impact of early and aggressive intervention after a warning stroke is not known.

This British study examined whether the creation of an urgent referral centre that would treat people with TIA and minor stroke earlier than a regular clinic, might reduce the risk of developing a new stroke in the three months after the initial symptoms.

What did this specialized clinic do for patients?

In addition to confirming the diagnosis of a warning or minor stroke, the team initiated or fine-tuned three kinds of treatments known to reduce stroke risk. The first involved medications that reduce the risk of clot formation (antiplatelets drugs often referred to as blood-thinners). The other two interventions consisted of administering drugs that lower cholesterol and blood pressure.

Another service offered by this clinic was the urgent ultrasound assessment of the carotid arteries to identify patients with significant narrowings who would benefit from surgery that improves circulation to the brain.

So, what did the study show?

The study was conducted in two parts. In Phase 1, researchers followed a group of about 300 patients who received routine care after a warning or minor stroke through a regular clinic. In Phase 2, after the creation of the specialized clinic, they followed a new group of 300 patients who were referred there and received prompt assessment. The researchers found that the risk of developing a new stroke in Phase 1 was 10 per cent, which fell to 2 per cent in Phase 2, a seemingly impressive 80-per-cent reduction.

One explanation for the findings is that the overall care of warning strokes improved over the years that the two study phases were conducted and this, in fact, was a factor in the reduced stroke rates observed.

Doesn’t this mean that these special TIA clinics should be a standard part of medical care?

No, or at least not yet. While the findings are intriguing, there are a number of problems that prevent this study from leading to sweeping changes in how warning and minor strokes are treated.

Most important to note is that this was not a randomized controlled trial. Such studies assure us that the patients assigned to the “new treatment” group and the ones who get the “usual treatment” are as similar as possible so that any difference in the findings of the study (new strokes in this case) can be viewed as being caused by the TIA clinic.

If these therapies are beneficial and recommended for general stroke prevention, what could the downside be?

The risk of over-treatment can be significant. Combining blood-thinners increases the risk of bleeding, and initiating one or more blood pressure-lowering medications can lead to such side effects as fainting and falls.

Although this study reports the risk of stroke at 90 days, a much longer follow-up is needed to see what the side effects are and whether these outweigh the benefits.

What’s the bottom line?

What we are sure of is that the risk of stroke after a warning stroke is significant. It is important that warning-stroke sufferers and their families recognize warning-stroke symptoms and seek urgent medical attention when they occur. Treatment decisions after a warning stroke need to be individualized, however, according to each patient’s risk of developing a stroke.

While it is too early to call for widespread creation of EXPRESS-type clinics, ongoing studies looking at precisely this issue are going to provide more reliable direction about what measures can best reduce the risk of a devastating stroke after suffering a warning stroke.

The authors thank Jeffrey Minuk, neurologist and stroke specialist at the SMBD Jewish General Hospital for his input.

The material provided in Healthwatch is designed for general educational purposes only and does not pertain to individual cases. The information included should not replace necessary medical consultations with your own doctor or medical professional.

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